The SLR treatment consists of refinishing the lifters to their specifications, next they are parkerized and finally polished to slide with the lowest friction possible in the lifter bores. SLR treatment is done to ensure all machined surfaces are within tolerances and the parkerizing guarantees the lifters will be compatible with ALL camshafts. These are USED German OEM lifters that have undergone the SLR treatment. Sold as set of 8. Other lifters are available, see related items.